1. Field of the Invention
The present invention generally relates to an X-ray detecting apparatus constructed of a scintillator array and a photodiode array. More specifically, the present invention is directed to an X-ray detecting apparatus including a film-shaped scintillator-channel separator capable of increasing sensitivity of the X-ray detecting apparatus.
2. Description of the Prior Art
In X-ray CT (computerized tomographic) imaging apparatuses such as a third-generation X-ray CT scanner and a fourth-generation X-ray CT scanner, X-ray detectors with scintillator arrays have been employed. Only a major construction of the typical X-ray detector is represented in FIG. 1. As shown in FIG. 1, this X-ray detector is mainly arranged by a scintillator array 10 and a photodiode array 20. The scintillator array 10 is constructed of a plurality of scintillator elements 11 and also a plurality of channel separators 12. Each of these scintillator elements 11 is sandwiched by the separators 12 at their side surfaces, thereby to constitute a scintillator channel. Then, a plurality of scintillator channels are constructed in an integral form. A reflection layer 13 is fabricated on an upper surface of the scintillator array 10, upon which an X-ray 100 is incident through a collimator 30.
The above-explained photodiode array 20 is fabricated on a substrate 21 in such a manner that a large quantity of photodiodes 22 are arranged at the same pitch, or interval as the channel pitch of the scintillator array 10. The respective photodiodes 22 are junctioned to a lower surface of the scintillator array 10 in relation to the respective scintillator elements 11.
On the other hand, the channel separator 12 employed in the scintillator array 10 has typically one function. That is, this function is to effectively conduct visible light produced within the relevant scintillator element to the corresponding photodiode 22, namely, an improvement in sensitivity.
The above-described scintillator X-ray detector is described in, for instance, Japanese Laid-open (KOKAI DISCLOSURE) Patent Application No. 58-118977 (opened on Jul. 15, 1983); No. 58-123488 (opened on Jul. 28, 1983); No. 58-216974 (opened on Dec. 16, 1983); No. 58-219471 (opened on Dec. 20, 1983); and No. 59-88676 (opened on May 22, 1984).
In general, a channel separator of a scintillator array employed in a conventional X-ray detector has been manufactured as follows:
1). White paint is coated as a light reflection layer on both surfaces of a heavy metal thin film made of, e.g., lead (Pb), tantalum (Ta), molybdenum (Mo), resulting in a first conventional channel separator. This prior art separator is sandwiched between side surfaces of the neighbour scintillator elements. PA1 2). A binder is mixed with titanium dioxide (TiO.sub.2), barium sulfate (BaSO.sub.4) or magnesium oxide (MgO.sub.2) to form a slurrying material. Then, this slurrying material is filled with a space between the neighbour scintillators elements and dried, resulting in a second conventional channel separator layer. PA1 a first thin film (2) capable of blocking transmission of the scintillation light occurring in the adjoining scintillator element channels; and PA1 first and second polymer sheets (1:101) each having first and second major surfaces, and capable of reflecting the scintillation light, said first thin film (2) being sandwiched between said first major surfaces of said first and second polymer sheets (1:101), and said second major surfaces of said first and second polymer sheets (1:101) being stucked to corresponding side surfaces of the respective adjoining scintillator elements (11), whereby said thin film (2) and said first and second polymer sheets (1:101) constitute the scintillator channel separator (120). PA1 a scintillator array constructed of a plurality of scintillator elements (11) for emitting scintillation light upon receipt of an X-ray; PA1 a photodiode array (20) constructed of a plurality of photodiodes (22) capable of detecting scintillation light emitted from said scintillator elements (11); and PA1 a scintillator channel separator (120) for optically separating scintillation light from each other within each of plural scintillator element channels of said X-ray scintillator array, said scintillator channel separator (120) including:
As to the first conventional channel separator, although the crosstalk preventing effect achieved by employing such a heavy metal thin film could be sufficiently high, the reflection layer coated with the white paint owns low reflectivity. As a consequence, there is a problem that sufficient X-ray detecting sensitivity could not be achieved. Furthermore, there is another drawback that the reflectivity characteristics of the white painted reflection layer are partially fluctuated due to uneven white painting.
On the other hand, in the second conventional channel separator layer, since transmittance of this channel separator with respect to visible light is on tile order of 1 to 5%, satisfactory crosstalk preventing effect could not be achieved. If a thickness of the second channel separator layer would be made sufficiently thicker, then the light crosstalk components could be satisfactorily suppressed. However, such a solution could not the accepted due to a practical reason. That is, the thickness of the second separator layers cannot be made very thick under the limited channel pitches, Moreover, since specific, high manufacturing techniques are required to manufacture such a second separator layer, higher manufacturing cost than that of the first conventional separator is necessarily required.